21123313512520 has 32 divisors (see below), whose sum is σ = 47528069311800. Its totient is φ = 8449216265728.

The previous prime is 21123313512493. The next prime is 21123313512523. The reversal of 21123313512520 is 2521531332112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 18449584908804 + 2673728603716 = 4295298^2 + 1635154^2 .

It is not an unprimeable number, because it can be changed into a prime (21123313512523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 238765 + ... + 6504124.

Almost surely, 2^{21123313512520} is an apocalyptic number.

21123313512520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21123313512520 is an abundant number, since it is smaller than the sum of its proper divisors (26404755799280).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21123313512520 is a wasteful number, since it uses less digits than its factorization.

21123313512520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6821217 (or 6821213 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 31.

Adding to 21123313512520 its reverse (2521531332112), we get a palindrome (23644844844632).

The spelling of 21123313512520 in words is "twenty-one trillion, one hundred twenty-three billion, three hundred thirteen million, five hundred twelve thousand, five hundred twenty".